Process of bonding carbon to aluminum



Jan. 12, 1960 R. R, PIKE m 2,920,385

PROCESS OF BONDING CARBON TO ALUMINUM Filed Feb. 8, 1956 United States Patent C PROCESS OF BONDING CARBON TO ALUMINUM Russell R. Fike, Euclid, and Albert J. Pilous, Cleveland, Ohio, assignors to Borg-Wamer Corporation, Chicago, 111., a corporation of Illinois Application February 8, 1956, Serial No. 564,200 16 Claims. (Cl. 29'472.7)

This invention relates to a process of bonding materials of different characteristics and more particularly to a process of bonding aluminum and its alloys to carbon and to the composite articles so produced.

Light metals, such as aluminum and its alloys, have found .wide acceptance where a great strength and rigid ity per unit weight is required, such as in the manufacture of aircraft parts, for example, bearings and pump bushings. While aluminum and its alloys provide good bearing surfaces, it is well known that carbon or carbonaceous materials offer superior bearing surfaces. Carbon, however, is quite frangible, but, by bonding the carbon to an aluminum or aluminum alloy member, a strong, lightweight, backing member is provided. Thus the useful life of the bearing is increased, since, if a cracking of the carbon occurs, the parts of the carbon bearing will 'be retained in position and still function as bearing surfaces. Particularly in aircraft installations the bearing need not be replaced immediately, such while the aircraft is in flight, and the parts within the bearings will still function in their proper manner. However, difficulties have been encountered in uniting aluminum and its alloys to carbon since a strong, perfect, bond is rarely attained. Therefore, the principal object of this invention is to provide a process of bonding aluminum and its alloys to carbon to provide a bond of maximum strength.

It is an object of the invention to bond or its alloys with carbon by means of a dissimilar metal having a melting temperature below that of the materials being bonded.

Another object of this invention is to provide a process of uniting aluminum and its alloys and a material, such as carbon, by the use of a low melting point metal.

A still further object of this invention is to provide an aluminum or an aluminum alloy housing with a carbon bearing surface.

These and other objects and features of this invention will become apparent from the following description when taken with the accompanying drawings, in which;

Figure 1 is a partial sectional view of a bearing member and housing formed in accordance with this invention; and

Figure 2 is a partial sectional view of the bearing of Figure 1 illustrating the bond in exaggerated form.

In its preferred form, the invention contemplates the provision of a structure comprising in part a backing member of aluminum or aluminum alloy, and in part a material such as carbon, which parts are united by means of a suitable low melting temperature agent, such as tin, to effectuate a strong permanent union in the na ture of a bond. The method in its preferred form broadly comprises the preparing of the aluminum or aluminum alloy body and the preparing of the carbon body and bringing the two bodies together at an elevated temperature to form the bond. The carbon is in the form of a mechanical shape, such as a cylindrical rod, a plate 2,920,385 Patented Jan. 12, 1960 like member, a bar, or other mechanical shape and is such that it is easily handled, as distinguished from finely divided or molecular particles or particles so small that their individual identity is substantially lost. The carbon must therefore be dense, free from voids impregnated oils, impregnated metals such as cadmium or zinc, or foreign matter of any kind that will not conduct current. Also, the carbon must not have the tendency to trap solutions. Impurities or irregularities, as described will result in a poor seal or make the process inoperative. In the preferred form comprises A.U.C. grade carbon, such as produced by the National Carbon Company.

Reference is now made to the drawings wherein there is illustrated a lined bearing member comprising a housing or sleeve 10 of aluminum or an aluminum alloy composed mainly of aluminum, a bearing liner or bush ing 11 of carbon, a flash or strike 12 of copper on the housing, a plating 13 of nickel on the housing, a flash or strike 14 of copper on the carbon, a plating 15 of nickel on the carbon, and a bonding agent 16 of tin, bonding the housing and the carbon liner. The platings are indicated at A and B, respectively, on the housing and carbon, in Figure 1. The preferred aluminum alloy is known as 17 S, and has a composition of 2.5% copper, 0.5% magnesium, 0.5% manganese and the balance aluminum. Of course, it is to be understood that other aluminum alloys having suitable properties may be used in the process. Also, the carbon may, within the purview of this invention, be bonded to the circumference of the housing, or may be a flat bearing surface bonded to some mechanical shape of aluminum or its alloys.

In making the structure just described, the aluminum or aluminum alloy part is first machined to the approximate shape and is prepared-for bonding, as follows:

(1) Degrease to remove cutting oils.

(2) Etch in 10% caustic soda for 10 minutes at room temperature.

(3) Rinse in Water at F.

(4) Dip in concentrated nitric acid for 5 to 15 seconds, or until smut is removed. i

(5) Rinse in cold water.

(6) Immerse in a caustic zincate bath for 15 to 45 seconds. The Work should be uniformly grey. If the work is spotty, repeat steps 4, 5 and 6.

(7) Rinse in cold water.

(8) Copper strike or flash.

(9) Rinse in cold water.

(10) Nickel plate 0.0002 inch minimum in a Watts type nickel bath with no brighteners.

(11) Rinse in cold water.

(12) Rinse in hot water.

(13) Dry.

(14) Apply a suitable flux to the metal and tin in molten tin at 550 to 700 F.

The carbon member must also be prepared for bond-- ing, as follows:

As soon as the two parts, i.e., the aluminum part and 9 the carbon part, are tinned, they are brought together underpressure, usually on the order of 2,000 p.s.i. and air cooled. The assembly is then ready for machining to its final dimensions.

With regard to the preparation of the aluminum or aluminum alloy and carbon shapes as set forth above, the copper and nickel plates on the members provide surfaces to which tin will adhere, since aluminum or aluminum alloys or carbon cannot be tinned directly. The copper is flashed onto the parts for good adherence and the nickel is plated thereon to a thickness of at least 0.0002 inch. The usual thickness of the nickel plate is 0.0005 inch. Nickel is employed as the final plating because it tins well and does not go into solution with the tin too rapidly, thus allowing time to heat the members to tinning temperature by immersion in the tin bath. No brighteners are employed in the nickel bath since they tend to make a plated metal brittle.

In tinning a material, it is usual to apply a flux to the parts prior to the tinning and a Du Pont product Eureka No. 55, a highly active and corrosive acid chloride type has been found satisfactory. However, other fluxes may be employed in the process, and it must be noted that no further flux is used after the parts are tinned; this procedure avoiding the trapping of flux at the interface.

The temperature employed to tin the parts may be in the range of 550 to 700 F. When the tin pot is large, temperatures of 550 to 650 F. may be employed. However, when the tin pot is small, that is, the volume of tin is small, temperatures of 600 to 700 F. are advantageously employed because the parts tend to extract heat from the molten tin very rapidly.

When the parts are assembled, it may be necessary to add additional tin therebetween, and such tin may be melted and flowed between the parts.

Although the bonding layer is referred to as being tin, it will be understood that a composition composed mainly of tin may be employed.

The resultant product is very adaptable for changing temperature conditions. For example, an essentially aluminum cylinder 1% inch outside diameter and inch inside diameter with a carbon line inch thick has been subjected to at least 20 thermal shocks (180 F. to 110 F.) and inspected thereafter. The structure showed no deterioration from the test to which it was subjected.

While the invention has been described within connection with several embodiments thereof, it is to be understood that this by Way of illustration and not by way of limitation and the scope of this invention is defined solely by the appended claims which should be construed as broadly as the prior art will permit.

' We claim:

1. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing at least one of said members with a layer of tin and assembling the members at a temperature in excess of the melting point of said layer comprising tin.

2. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing the first and second named members each with a layer comprising tin, and assembling the members at a temperature in excess of the melting point of said layer comprising tin.

3. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing at least one of said members with a layer of nickel, providing at least one of said members with a layer comprising molten tin, and assembling the members while the layer comprising tin is in molten condition.

4. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing each of said members with a layer of nickel, providing each of said members with a layer comprising molten tin,

3 racemes A and assembling the members while said layers comprising tin are in molten condition.

5. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing each of said members with a layer of nickel, applying a flux to each of said members, providing each of said fluxed members with a layer comprising molten tin, and assembling the members while said layers comprising tin are in molten conditions.

6. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing each of said members with a layer of nickel having a thickness of at least 0.0002 inch, tinning each of said members at a temperature of 550 to 700 F. and assembling the tinned members at a temperature of 550 to 700 F.

7. A process of bonding an aluminum or aluminum alloy member to a carbon member, comprising, providing each of said members with a layer of nickel having a thickness of at least 0.0002 inch, applying a flux to each of said members, tinning each of said members at a temperature of 550 to 700 F., and assembling the tinned members at a temperature of 550 to 700 F.

8. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, degreasing and cleaning said first named member, providing said first named member with an electro-deposited layer of nickel having a thickness of at least 0.0002 inch, cleaning and degreasing said carbon member, providing said carbon member with an electro-deposited layer of nickel adding a thickness of at least 0.0002 inch, tinning each of said members at a temperature of 550 to 700 F., and assembling the tinned members at a temperature of 550 to 700 F. while applying pressure thereto.

9. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, providing each of said members with a copper strike, providing each of said members with a layer of nickel, applying a flux to each of said members, tinning each of said members, and assembling said tinned members while said tin is in molten condition.

10. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, degreasing and cleaning each of said members, providing each of said members with a copper flash, providing each of said members with an electro-deposited layer of nickel having a thickness of at least 0.0002 inch, tinning each of said members at a temperature of 550 to 700 F., and assembling said tinned members at a temperature of 550 to 700 F. while applying pressure thereto.

11. A process of bonding an aluminum or aluminum alloy member to a carbon member comprising, degreasing and cleaning each of said members, providing each of said members with a copper flash, providing each of said members with a layer of nickel having a thickness of at least 0.0002 inch, applying a flux to each of said members, tinning each of said members at a temperature of 550 to 700 F., and assembling the tinned members at a temperature of 550 to 700 F. while applying pressure thereto.

12. The process of constructing a bearing having a housing of aluminum or its alloys and a bushing of carbon comprising, the steps of providing the surfaces of said housing and said bushing to be joined with a layer of nickel, tinning the surfaces of said housing and said bushing to be joined, and assembling the tinned surfaces at a temperature in excess of the melting point of tin.

13. The process of constructing a bearing having a housing of aluminum or its alloys and bushing of carbon comprising, the steps of providing the surfaces of said housing and said bushing to be joined with a layer of nickel, tinning said surfaces, and assembling the said tinned surfaces at a temperature in excess of the melting point of tin and below the melting and said bushing.

14. The method of constructing a bearing having a housing of aluminum or its alloys and a bushing of carbon comprising the steps of providing the housing and bushing surfaces to be joined with a layer of nickel having a thickness of at least 0.0002 inch, tinning the surfaces at a temperature of 550 to 700 F., and assembling the tinned surfaces at a temperature of 550 to 700 F.

15. The method of constructing a bearing having a housing of aluminum or its alloys and a bushing of carbon comprising the steps of providing the surfaces of said housing and said bushing to be joined with a copper flash, providing said surfaces with a layer of nickel having a thickness of at least 0.0002 inch, applying a flux to said surfaces, tinning said surfaces at a temperature of 550 to 700 F., and assembling said surfaces at a temperature of 550 to 700 F.

16. The method of constructing a bearing having a housing of aluminum or its alloys and a bushing of point of said housing 6 carbon comprising the steps of degreasing and cleaning said housing and said bushing, providing the surfaces of said housing and said bushing to be joined with a copper flash, providing said surfaces with a layer of nickel having a thickness of at least 0.0002 inch, applying a flux to said surfaces, tinning said surfaces, and assembling the tinned surfaces at a temperature of 550 to 700 F.

References Cited in the file of this patent UNITED STATES PATENTS 1,314,603 Mott -L Sept. 2, 1919 2,228,352 Mopfield Jan. 14, 1941 2,256,272 Batcheller Sept. 16, 1941 2,333,622 McNab Nov. 2, 1943 2,361,157 Thompson et a1 Oct. 24, 1944 2,386,628 Nazzewski Oct. 9, 1945 2,478,656 Dutterer Aug. 9, 1949 2,637,686 McKay May 5, 1953 2,686,958 Eber Aug. 24, 1954 2,798,577 La Forge July 9, 1957 

1. A PROCESS OF BONDING AN ALUMINUM OR ALUMINUM ALLOY MEMBER TO A CARBON MEMBER COMPRISING, PROVIDING AT LEAST ONE OF SAID MEMBERS WITH A LAYER OF TIN AND ASSEMBLING THE MEMBERS AT A TEMPERATURE IN EXCESS OF THE MELTING POINT OF SAID LAYER COMPRISING TIN. 